In the conventional manufacturing process for brushes, particularly toothbrushes, the brushes are injection molded with empty tuft holes in the toothbrush head. The tuft holes may also be drilled after the injection molding as well as initially formed in the head concurrently with the injection molding. In a secondary operation, U shaped tufts of bristles are inserted into the holes in the head. Each tuft of bristles is held in place by a plate-like staple that is wider than the tuft hole so that when the staple is used to drive the U-shaped bristle tufts into the tuft hole, the edges of the staple slightly cut and deform the sides of the hole. The pressure and resulting static friction of the surrounding plastic on the staple contributes to forces maintaining the staple in place. However, there are certain problems associated with brushes made in this manner. Specifically, individual bristles, or even entire tufts of bristles, may occasionally come out of the tuft holes during brushing by a consumer. The staple or anchor art has dealt with these problems in a variety of ways. However, adequately securing tufts of bristles within the tuft holes must be balanced against other considerations, such as costs of materials and the ability to mass manufacture product.
Over the years, toothbrush staples of the rectangular type have become available in which at least one of the major surfaces thereof is provided with parallel horizontal grooves (i.e. grooves that extend parallel with a longitudinal axis of the staple), thereby yielding a staple that has been found to be more resistant to becoming separated from its tuft hole than staples with smooth surfaces.
Staples have also been developed having a rounded edges that eliminate and/or minimize the problem of tuft weakening and possible rupture of filaments or bristles at the bight of the U. With such a rounded construction, the zone or area of contact between the lower staple edge and the bristle filament closely matches the U shape at the bight portion of each tuft. In turn, this permits the staples to be driven deeper into the head and thus a larger and more consistent force can be applied to each U shaped tuft without cutting or damaging the filaments.
More recently, staples having specialized groove patterns on the major surfaces of the staples for improved retention, including a slanted configuration of parallel grooves, have been introduced to the art.
Staples constructed of materials having oligodynanic action have also been disclosed in the art. These oligodynamic staples have smooth major surfaces and are constructed of a material having oligodynamic action, such as cadmium, silver, brass, copper, stainless steel, titanium and mercury.
Typically, toothbrush staples are constructed of a nickel-silver alloy. Due to the costs associated with the nickel-silver alloy, it has long been desired to create staples from cheaper metals, such as brass. While the general concept of using a brass staple has been disclosed, testing and experimentation have proven that merely creating and using a flat-faced brass staple cannot be used in the manufacture of toothbrushes to provide effective tuft retention. Moreover, merely applying known groove patterns has also proven to be ineffective.